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A Feedback Control Architecture and Design Methodology for Service Delay Guarantees in Web Servers

Lu, Chenyang; Abdelzaher, Tarek; Stankovic, John; Son, Sang
Lu, Chenyang
Abdelzaher, Tarek
Stankovic, John
Son, Sang
This paper presents the design and implementation of an adaptive architecture to provide relative, absolute and hybrid service delay guarantees for different service classes on web servers under HTTP 1.1. The first contribution of this paper is the architecture based on feedback control loops that enforce delay guarantees for classes via dynamic connection scheduling and process reallocation. The second contribution is our use of feedback control theory to design the feedback loop with proven performance guarantees. In contrast with ad hoc approaches that often rely on laborious tuning and design iterations, our control theory approach enables us to systematically design an adaptive web server with established analytical methods. The design methodology includes using system identification to establish dynamic models for a web server, and using the Root Locus method to design feedback controllers to satisfy performance specifications. The adaptive architecture has been implemented by modifying an Apache web server. Experimental results demonstrate that our adaptive server provides robust delay guarantees even when workload varies significantly. Properties of our adaptive web server also include guaranteed stability, and satisfactory efficiency and accuracy in achieving desired delay or delay differentiation.
University of Virginia, Department of Computer Science, 2001
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